docstr: replaces string at index idx in list `tokens` with a masked token and returns the modified list. 
docstr_tok: ["replaces","string","at","index","idx","in","list","`","tokens","`","with","a","masked","token","and","returns","the","modified","list","."]
code: def __mask_text__(self, idx: int, tokens: List[str]):
      """
      replaces string at index idx in list `tokens` with a masked token and returns the modified list.
      """
      masked = tokens.copy()
      masked[idx] = self.MASK_LABEL
      return masked
  
file_path: NeMo/nemo/collections/common/parts/mlm_scorer.py
imports: from typing import List
  import numpy
  import torch
  from torch.nn.functional import softmax
  from transformers import AutoModelForMaskedLM, AutoTokenizer
label_desc: Use image node_id 4 for calling the MLMScorer obj's underlying member method code with example usage: obj.__mask_text__(idx, tokens) and returns: masked